Wear indicating device for drill bits



Jan. 1, 1952 J. c. s'roKEs WEAR INDICATING DEVICE FOR DRILL BITS Filed March 4, 1949 2 SHEETS--SHEET l 2 SHEETS-SHEET 2 J. C. STOKES WEAR INDICATING DEVICE FOR DRILL BITS Jan. l, 1952.

Filed March 4, 1949 doh/7 C. J70/fes .IA/VENTURI ATTORNEYS Patented Jan. 1, 1952 UNITED .STATES PATENT OFFICE WEAR INDICATING DEVICE FOR DRILL BITS J ohn C. Stokes, Houston, Tex., assignor to Reed Roller Bit Company, Houston, Tex., a corporation' of Texas Application March 4, 1949, Serial N0. 79,547

7 Claims. (Cl. Z55-61) This invention relates to new and `useful improvements in wearindicating device 'for drill bits.

In well drilling, maximum emciency is obtained when the drill bit, which is attached to the lower end of the drill pipe, is used until it is substantially dull and is' no longer capable of performing the drilling operation. Because the bit is carried by the lower end of the drill pipe, it is apparent that the removal of said bit involves removal of the entire drill pipe string which is an expensive operation, requiring considerable time and labor. Thus, if the drill bit is removed before it has been dulled, an unnecessary removal of the drill pipe string'has occurred.` If, on the other hand, the drill bit is not removed when dull, drilling efficiency is impaired.

It has heretofore been the practice to rely solely uponthe driller and his particular knowledge based on experience with respect Vto the time when the drill bit had dulled and should be removed `and obviously, the human element of error has always been presentwith the result that in many instances, the bit is pulled or removed from the well either prematurely or too long after the bit has lost its drilling eiliciency. Furthermore, the driller depends solely on feel in making his decision as to removal of the drill bit any many variable conditions which may occur in the well bore become factors which cause erf rorrwregardless of the experience of the driller. Therefore, because the determination of the dullness of the bit has been based on the personal or-individual opinion of the driller many errors of judgment constantly occur and result in erroneous withdrawal of the bit, thereby increasing the cost and reducing the eiliciency of the over all drilling operation.

It is one object of this invention to. provide an improved indicating device which will automatically signal to the surface when the drill bit is worn to a predetermined point, whereby accurate information as to the condition of the drill bit is made known to the driller or operator.

An important object of the invention is to provide a wear indicating device for drill bits wherein the pressure of the drilling uid is utilized as a signalling medium and also wherein a sudden variation in said pressure is indicative of the factA that the bit has been worn to a predetermined point.

A further object is to provide a'device, of the character described, having means for causing a relatively small pressure variation in the circu- 2 lating fluid when the drill bit wears to a prede-V termined point, together with means for utilizing the small pressure variation to actuate apparatus which causes a relatively large pressure variation in the circulating uid, whereby the pressure. variation is clearly noticeable as a signal at the surface. l vStill another object is to provide an improved indicating device which may be readily applied to a drill bit of ordinary construction and which includes a normally closed wear tube located ex-v teriorly of the bit and communicating with the drilling fluid circulating through the bit body; said tube having. such length and being so disposed that the normal drilling operation will wear said tube to open the same when the bit hasworn to a predetermined point, whereby a pressuredrop in the circulating fluid occurs as soon as said tube is opened, which pressure drop may be utilized to signal to the surface. Y .Y

Anotherobject is to provide a. device which lends itself to ready adjustment so that a signal may be transmitted to the surface when the bit is completely worn or -when therbit has worn to any predetermined point at which itmay be desirable to remove said bit.

A particular object of the invention is to pro-- vide an improved device, ofthe character described, having a relatively large, normally closed discharge port which is mounted inthe drill bit body and which is subjected vto the pres--,v sure of the circulating drilling iluid, together ,l

with means for opening said port when thedrillbit has worn to a predetermined point, whereby a sudden relatively large drop in the pressure of the circulating drilling fluid occurs to immediately signal the condition ofthe bit to the surface in' n a noticeable manner. Y t

'Other and further objects of this invention will appear from the following description.

In the accompanying drawings which form a' part of the instant specification and which are` to be read in conjunction therewith and wherein`- 1 like referencenumerals are used to indicate like:

parts in the various views:

Figure 1 is an elevation of a drill bit having the improved indicating device constructed in accordance with the invention mounted thereon,I

Figure 2 is a bottom view of the drill bit,

Figure 3. is a transverse sectional .viewof the' indicating device taken on the line4 3'-3, of Figure' v.1 and showing the device before actuation, Figure 4 is a view similar to Figure-tilillustrating the 'position of the parte whengthewear tube' has been opened due to the wearing of the bit blades to a predetermined point, and

Figure 5 is a View similar to views 3 and 4, illustrating the signalling port completely open.

In the drawings, the numeral It designates a bit body which has the usual threaded box II at its upper end whereby the bit may be connected to the lower end of the drill pipe or stem. The usual fluid cavity I2 is formed in the bit body and cutting blades I3 are welded or otherwise secured to the lower portion of said body. Drilling duid circulating passages I4 extend from the cavity I2 and discharge from the lower portion of the body adjacent the blades I3 (Figure 2). As illustrated, the blades I3 are disposed transversely of the bit body and have their lower cutting edges I3a located in a plane below the lower end of the body. When the cutting blades have been worn through the drilling operation to approximately the line indicated at A in Figure 1, it is desirable that the bit be replaced, for at this point said bit is completely dulled. I 'For indicating that the bit blades I3 are worn down. to the vpoint indicated by the line A, the improved indicating device B is arranged to be mounted on the bit body IB. This device includes an annular sleeve or cylinder I5 which isl threaded into an opening I6Y in the wall lila ot the bit body; The outer portion of the sleeve. which extends outwardly from the body may be of angular or hexagonal shape as indicated at I'T to facilitate rotation of the sleeve or cylinder' by means of a; suitable wrench.

The sleeve or cylinder I5 is formed with an axial bore- I8 which extends' entirely therethrough and the inner end of the bore is open to the: cavity I2l within the `bit body whereby the drilling' iiuid which is circulated through the cavity may flow into the inner end oi' the sleeve of cylinder. The outer endv of the bore I8 of thev sleeve is closed by a metallic disc I9 which isv weided or brazed in position against an internal shoulder 28 formed' within the bore. The disc has a relatively thin wall and has suilicient strength to withstand the pressure of the drill' ing fluidwhich i's normally circulated through the cavity I2 during the drilling operation. A Wear tube 2f has its inner end mounted and suitably fastened, as by weld-ing, within a radial opening 22 formed in the wall of the sleeve or cylinder t5- and the outer end 'of the. tube ist.

closed as indicated at 23. Thus, the drilling huid which. is. circulated through the cavity I2'.

intoy thetube 2I tial alignment with the. line; A and, said tube extends contiguous to the trailing face of one of the blades I3, being spaced inwardly from the outer vertical edge. |322 of the bit blade. Thus, during normal. drilling operations the wear tube 2.Il is uneiiected and it4 is-only whenk the lbit blades l3- are worn downto the. point indicated by the line A that the end of the tube 2,3 isv subjected to any abrasive act-icm Upon wearing down of the blades to the line A a subsequent rotation of the, bit resul-ts in a wearing away of the closed end 23 of the tube 2l'.

To eilect a considerable variation in the pressure ofthe circulating drilling duid when thek wear tube 2|' is open and thereby provide a signal at the, surfe/ca a piston member. 24 is mounted within the bore I8 of the sleeve orv cylinder I5. This pistonA member is illustrated as a hanged cup havingk an axially disposed punch` 25 formed integral therewith. Restricted equalizing orifices `2li Yare provided in the base of the piston member,` whereby when the end 23 of the wear tube Y shoulder I8a which is provided at the inner end of the bore of the sleeve or cylinder. The punch 25 has a lower pointed end which is suilicientlysharp to puncture. the closure disc I when the piston 24, is moved. under a predetermined force against` said disc.

In the operation of the device, the assembly is mounted on the body I of the drill bit with the sleeve or cylinder i being threaded into the opening I6 in the bit body. The wear tube 2l has its lower end 23 closed and vsaid tube has. a pre-determined length whichdisposes this lower closed end in a plane opposite the line to 2which the cutter blades,l3 of the bit will be worn bee vfore a signal is given. With the, wear tube having its end closed the drilling fluid within the cavity I2 may enter the inner end of thev cylinder and may passV through the restricted orifices 26 to enter the bore I 8' between the piston 24 and the closure disc I8 and to also enter the interior of the wear tube 2l'. Normal drilling is carried out withv the drilling fluid being circulated down.- wardly through the drill pipe (not shown), and cavity l2, and through the discharge ports I4 ofV the bit. As has been stated, thek closure discA I8' is of sunicient strength to stand the normal pressurev of the circulating fluid during the drilling operation and since the wear tube is disposed contiguousl to the rearV face of the bit blades and is actuallywithin the confines of the exterior surface of' the bit body as shown in Figure 2, said tube will not be subjected to any wear during such normal drilling. As the bit blades I3 become worn through drilling until saidblades wear to the plane indicated by the line A, which is in the same plane as the lower end 23 of the wear tube, the abrasive action of the formation against the closed end 23 of the wear tube 2l will result in a wearing away of said end 233 whereby the wear tube is opened. As soon as the end 23 of the tube is worn to open' said tube, the fluid withinthe tube and also within the bore of the cylinder I5 between the closure disc' IS- and' piston 24 is released and may flow outwardly into the well bore. Because of the restricted orifices 26 there is an immediate pressure differential set up across the piston 2'4' and the considerably higher pressure of the. drilling fluid within the cavity I2 of the drill bit will move the piston outwardly with sufficient force to cause the punch tor puncture the; closure disc I'S. as illustrated in The abrasive actiony of this fluid under pressure passing through the relatively restricted open ings 26. in the piston and the opening 21 in the, disc. will result in a. rapid wearing awa-y. of the` base of the piston and of the closure disc. Thus, in a relatively short period after the. closure disc I9 is punctured, said. disc and the. piston, 2.4 are completely displaced to entirely operi the en larged bore-I8 `of the cylinder or sleeve. Complete opening of this relatively large bore results a considerable pressure drop in the pressure of the fluid being-circulated downwardly through thedrill pipe (not` shown), and the cavity. i2 and this pressure drop provides an indication at the surface which. advises the driller that the bit blades-have worn down to a predetermined point and that replacement of the bit is advisable.

It is pointedout that the arrangement provides the relatively small tube 2| which is desirable because the smallerY tube may be mounted in close relationship to the bit body and danger of accidental severing or breaking oif thereof during normal drilling is substantially eliminated.

However, the smaller tube has the disadvantagek erroneous indication. The present device contemplates the use of a small tube which when opened functions to actuate the piston 24 and thereby open a larger bore so that an ample pressure drop for signalling purposes will occur in the circulating uid.

The invention is shown as applied to the usual blade type drilling bit but it is apparent that the device may be employed with any of the ordinary bits now in general use. It is, of course, desirable that the lower end of the wear tube 23 be disposed in the plane to which the cutting members are worn when the bit is dull, but there may be instances where it is desired to remove the bit before it is completely dull; in such case, it is only necessary to vary the length of the tube 2i so as to locate its closed end 23 in the desired plane.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having described the invention, I claim:

l. The combination with a drill bit having cutting elements and having a drilling fluid circulating therethrough, of a wear indicating device including, an annular member mounted in the body of the bit and having its inner end communicating with the interior of the bit body whereby the drilling fluid may enter said member, a closure normally closing said member, and a fracturing means within the member and operable when the cutting elements have worn to a predetermined point to open said closure and allow ow through the member to cause a variation in the pressure of the circulating uid.

2. In combination, a drill bit having cutting elements and also having an opening in the wall of its body, means for circulating a pressure drilling fluid through said bit, a wear indicating assembly mounted in the opening in the drill bit body and including, a cylinder, a closure for clos'- ing the outer end of said cylinder, piston means within the cylinder adapted to move into engagement therewith to fracture said closure, means for maintaining said piston means normally in a position adjacent said closure byan equalization of pressures thereacross, and meansactuated when the cutting elements have been worn a predetermined amount by a drilling operation for unbalancing pressures across'said fracturing means, whereby said` means is movedinto engagement with the closure to fracture the same and thereby allow flow through the opening-in the bit body to'vary .the pressure of the drilling uid circulating through theV bit.

3`. A wear indicating device" 'adapted to vbe mounted on a drill bit including, anannula'r supporting member mounted in the body of thefbit and having its bore communicatingfwith the 'pres'- sure drilling iiuid within the bit body, a closure for the outer end of the member, a wear tube extending from the member and having one en`d` communicating with the bore thereof and-its op'"" posite end normally closed, the closed end of said wear tube being adapted to be opened when the drill bit cutting elements have worn a predetermined amount, and piston means within the annular supporting member movable into engagement with the closure when the end of the wear tube is opened to open said closure and allow flow through said member and thereby produce a drop in the pressure of the drilling fluid within the bit body.

4. The combination with a drill bit having cutters and having a pressure drilling fluid circulating therethrough of a, wear indicating device including, a wear element mounted exteriorly of the body and having its inner end communicating with the pressure uid within the bit, the outer end of said element being closed and being disposed in a predetermined plane with respect to the cutters of the bit, whereby after said cutters have worn a predetermined amount the closed end of the element is also worn and is thereby automatically opened, the bit body having an enlarged passage therein, a closure for said passage, and piston means within the passage and engageable with the closure when the wear element is opened to remove the closure and allow flow of the'pressure drilling fluid through said passage, whereby a pressure variation is caused to occur in the drilling nuid.

5. In combination, a drill pipe, a drill having drilling cutters mounted cn the lower portion of said pipe, means for circulating a pressure drilling fluid through said pipe and through a passage in said bit, means normally closing said passage in the bit, means for causing a relatively small pressure drop in the pressure of the circulating drilling fluid when the cutters have worn a predetermined amount, and a movable piston within the bit passage actuated by the relatively small pressure drop to remove the closure and open the passage and thereby effect a relatively large drop in the pressure of the circulating drilling iiuid, whereby a signal of the wearing of the cutters to said predetermined point is given at the surface.

6. In combination, a drill pipe, a drill bit attached to the lower end of the pipe and having cutters thereon, means for circulating a pressure drilling fluid downwardly through said pipe and bit, the body of the bit having a cylinder 'ahem-Sco therein. la. closure for yone end of said cylinder, a lpiston member adjacent said opening and having means :for puncturing said closure, said member normally having opposite sides exposed to the pressure of the .circulating fluid and disposed i111 spaced relation to the closure, and a wear tube having a closed end communicating with the area between the piston member and closure, said Wear tube being opened to unbalance pressures across the piston when the cutters of the bit have worn a, predetermined amount, whereby the pressure of the drilling Yfluid may act upon the piston to move the same into engagement with the .closure to puncture the Same and thereby allow `a flow of drilling duid through the Aopening to reduce .the pressure of'said uid within the 'bit and pipe and provide a sig-nal at the surface.

7. In combination, a drill pipe, a vdrill bit attached to the lower end of the pipe and having cutters thereon `and `also having a passage extending outWa-rdly through the Wall thereof, means for circulating a pressure drilling ud downwardly through LSaid pipe and bit, a cylinder within the passage, a kclosure closing the outer end ci said cylinder, a piston within the cylinder and having means 0,11 that side adjacent the elo.- sure for puncturing ,said closure, said Apiston also having openings therethrough whereby pressures thereacross may be equalized, and Ia wear tube extending' from the cylinder exteriorly of the bit and communicating with the area between the piston and the closure, the outer end of said wear tube Vbeing closed and being adapted to be opened by Wear when the cutters of the bit have Worn a predetermined amount, whereby the area `between the piston and closure is opened to unbalance pressures across Athe piston and thereby move said piston `into engagement with Athe olosure to open the same.

JOHN C. STOKES.

REFERENCES CITED The following references are of record in the file of this patent:

Number Name Date 1,508,443 kChristian Sept. 16, A1924 2,239,106 Krall Apr. 22, 1941 2,461,164 Lewis Feb. 8, 1949 2,489,687 Thrift et a1. Nov. 29, V1949 2,560,328 Bielstein July 10, 1951 2,562,833 True July 31, 1953. 

